Injectable drugs are necessary for numerous medical reasons, and they are typically used in a wide variety of applications. Consequently, various types of drug delivery systems have been developed to meet the many diverse needs of particular medical procedures. With any injectable drug delivery system, however, both physical and psychological implications are involved. Both are important, and both deserve consideration.
In general, all injectable drug delivery systems require some mechanical device or system that will drive or force a liquid into the body of a person or animal. Typically, this can be done in either of two ways. One way is to use a hypodermic needle. The other requires the use of a so-called needleless injector that relies on a liquid jet to create a hole in the skin. The liquid (i.e. fluid medicament) is then forced through the hole and into the body. Although needleless injectors are particularly efficacious for subcutaneous injections, they typically require excessive power to achieve the depth normally required for many intramuscular injections. With the above in mind, the focus here is on drug delivery systems that require the use of a hypodermic needle.
The physical implications that are involved when a hypodermic needle is used with an injectable drug delivery system pertain primarily to the needle itself. The length, the diameter and the needlepoint characteristics of a hypodermic needle are all obvious considerations in this context. Collectively, during the development of an injectable drug delivery system, these considerations must be engineered to: 1) establish the proper depth of an injection; 2) avoid a tissue compression, that will either cause a deep injection or result in needlepoint deformation due to bone contact (i.e. “fish hook”); 3) minimize the dangers of handling needles; and 4) allow for effective insertion of the needle into the body. An improper engineering of some, or all, of these considerations may affect drug absorption rates or cause pain. Apart from these considerations, however, the psychological implications that result from using a hypodermic needle may be even more profound. This is particularly so when the fluid medicament is to be self-administered.
Like the physical implications noted above, the psychological implications that are involved when a hypodermic needle is used with an injectable drug delivery system pertain primarily to the needle. Needle anxiety is real. For instance, many patients have a natural aversion to even the sight of a needle. Further, this aversion frequently evokes fear of injection site reactions (e.g. pain and bruising) that may, or may not, be real. And, when the injection needs to be self-administered, the task itself will often cause a hesitation or paralysis on the part of the user that prevents accomplishing a proper injection. In this context, it is known that “needle anxiety” has caused some patients to unnecessarily delay the beginning of a therapy regime for extended periods of time (e.g. several years).
Several attempts have been made to overcome many of the aforementioned implications that are associated with injectable drug delivery systems. For one, there have been efforts to provide so-called auto-injectors that will automatically drive a needle attached to a syringe into the skin to perform an injection. Typically, this is a push-button operation that is accomplished without any direct manipulation of the injector's drive mechanism. Nevertheless, prior to use, auto-injectors invariably involve many complicated steps for set-up. And, after use, they require special disposal procedures for the needle. Unfortunately, these operations typically expose the user to a visual contact with a needle that can trigger “needle anxiety.” Also, injections with an auto-injector can be perceived to be more painful than a regular syringe injection due to the auto-injector's response to the drive mechanism actuation. Further, auto-injectors are typically not configured to conveniently provide for the sequence of multi-dose injections that may be required for many treatment regimes.
In light of the above, it is an object of the present invention to provide an auto-injector that is convenient to use and that requires minimal manipulation before, during, and after an injection. Another object of the present invention is to provide an auto-injector that overcomes needle anxiety by keeping the needle(s) hidden from patient-view at all times. Still another object of the present invention is to provide an auto-injector that conveniently uses a “clip” or “magazine” of sterile needles to eliminate operating steps, and to allow a patient to follow a multi-dose treatment regime wherein a new sterile needle is automatically provided for each injection. Yet another object of the present invention is to provide an auto-injector that automatically captures used needles and stores them out-of-sight for a subsequent safe and simple disposal with regular trash. Another object of the present invention is to provide an auto-injector that is easy to use, is relatively simple to manufacture, and is comparatively cost effective and provides a comfortable injection.